op pittsburgh



Feb. 3, 1931. F. c. LA MAR 1,790,713

RENEWABLE ELECTRIC FUSE Original Filed Jan. 5. 1927 m E 12 i i \14 15+ Tfzo 15 n I I I. ii v|v| 1Q ll VENTOR.

wvzaw Patented Feb. 3, 1931 UNITED STATES PATENT OFFICE FRANK C. LA MAB, OF PITTSBURGH, PENNSYLVANIA. ASSIGNOR TO GREAT WESTERN FUSE COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF DELAWARE RENEWABLE nnnc'rmc FUSE Application filed January 5, 1927, Serial No. 159,080. Renewed December 15, 1930.

More particularly my invention relates to the type of fuses which are provided with blade terminals.

In fuses of this type in case of the burning out or fusing of the fusible element, the generated gases tend to escape along the blade terminals with the result that the terminals are frequently fused, or welded to the clips or other attachments either by the high temper-ature of the escaping gases or by the deposit of particles of the metal of the fusible element or elements carried by the gases, and a like welding frequently takes place between the end parts of the fuse which are designed to be in easy removable relation to facilitate reloading.

Attempts have been made to provide a'gastight joint for the blade terminals by means of felt or other packing but the result has not been satisfactory and the use of such materials in electric fuses is now regarded as highly objectionable.

The object which I have in view is the prevention of this escape of the gases and the provision for the gases of a restricted and well distributed lateral escape.

For this purpose I provide a sealed engagement between the blade terminals and their anchoring means.

To facilitate the escape of the gases I also provide for restricted and widely distributed escape between the cap and the ferrule.

In the accompanying'drawings, wherein I have illustrated the best embodiment of the 3? principles of my invention now known to me, Fig. 1 is a side elevation of the fuse, the same being partially broken away in longitudinal section to show parts otherwise concealed; Fig. 2 is an end view of thefuse with the cap removed; Fig. 3 is an enlarged diametric section showing the ferrule, the cap and the terminal of the fusible element, and F ig. 4 is a view similarto Fig. 3 but taken in a plane at right angles to Fig. 3.

Referring to the drawings, 1 represents the usual shell of insulating material, such as fibre, on each end of which is mounted a metal, preferably brass, ferrule 2. The ferrules are commonly secured to the shell by means of -30 their internal threads 3 which screw onto the externalthreads 4 on the ends of the shell. The ferrules are preferably fixed in position as b means of the rivets 5.

T e outer portion of each ferrule is of reduced external diameter, thus forming a circumferential shoulder 6, and such outer portion is exteriorly threaded as at 7 to receive the metal or brass cap 8 whose skirt is provided with the internal threads 9. The inner end of the skirt is channelled orgrooved, as at 10 to the full de th of the threads 9.

11 represents the usible member which occupies the shell 1 and has attached to its ends, as by means of the bolts 12, the blade terminals 13. In the larger sizes of fuse it is usual to provide a plurality of fusible members arranged in parallelism and all connected at their ends to the same terminals. The fusible members are of suitable material and the terminals are preferably brass. Said terminals are provided with inwardly facing shoulders 14 at each edge and inside of said shoulders are mounted the rectangularabutment plates 15 which are fixed in position relative to the terminals.

Each of the ferrules 2 is provided with an interrupted head or outer end web 16, the same being cut away to form the larger opening 17 through which the fusible member and its terminals may be inserted or removed, while at the opposite side of the web there is a smaller opening 18 which with the opening 17 provides for the free escape of the gases from the shell 1. Intermediate of said openings is a third opening 19 which has parallel ends and at one side the interrupted side Walls which separate it from the smaller opening 18.

WVhen the terminal 13 is in place the abutment plate 15 fits in the opening 19 and the terminal is thus held in position, the shoulders 14 extending over the ends of the opening 19.

Between the abutment plate 15 and the shoulders 14 an apertured washer 20 is mounted and fixed on the terminal, said washer 20 providing a ledge which extends outwardly beyond the terminal all around the same and at the ends extends over the abutment plate 15. When the terminal is in position, the 100 jee ends of the washer 2O overlap from without the ends of the opening 19 and bear against the web 16 of the ferrule at each end of the opening 19, thus preventing an inward movement of the terminal.

It is evident that the terminal may be released by shifting it laterally into the larger opening 1'( and that it may be locked in place by shifting it from the opening 17 to the opening 19.

The web 16 is preferably sunken sli htly below the end of the ferrule 2 as shown, and when in position the washer 20 protrudes slightly beyond the end of the ferrule.

21 is the circular washer slotted as at 22 to be slipped down over the blade of theterminal 13 against the fixed washer 20. The washer 21 may be provided with the usual inwardly extending toes or studs 23 which engage with the edges of the web 16 to prevent rotation of the slotted washer. The cap 8 is of annular form having an inwardly extending lip 24 which engages the washer 21 as the cap is screwed onto the ferrule. The lip 2- 1 is slightly undercut so that the lip bites on the washer 21 with its annular inner edge.

t is evident that .the tightening of the cap on the ferrule will clamp the slotted washer 21 snugly down on the fixed washer 20 and thus form a gas-tight joint around the blade terminal .18 which will prevent the. axial escape of the gases along the terminal.

It is also evident that the annular inner edge of the lip 2a of the cap 8 will form a gas-tight joint with the washer 21, thus preventing the material escape of gas between the washer and the cap.

It is further evident that the washer 21 will not be forced down into tight contact with the end of the ferrule 2 so that the gases. will find a restricted escape by means of the channel 10 and between the meshed threads of the cap and the ferrule, such escape being distributed for the full perimetral surface of the ferrule. The skirt of the cap is short enough to prevent contact with the shoulder 6 of the ferrule so as not to interfere with the escape of the gases.

It is evident that the gases are thus prevented from axial escape but that the gases are provided with means for their lateral escape over a widely distributed area comprising the full perimetral extent of the threaded engagement of the cap and ferrule.

By this means I am enabled to do away with the felt or other packing which is sometimes employed to reduce the axial escape of the gases.

The threaded engagement between the cap and the ferrule is preferably loose enough so that there is no danger of the cap being frozen in place when a reloading is required.

What 1 desire to claim is 1. In renewable electric fuses of the blade terminal type, the combination of an insulating shell, a ferrule on the end of the shell,

said ferrule having an apertured head, a fusible element, a blade terminal provided with abutment means for engaging the apertured head of the ferrule, aslotted washer slipped down overthe blade, a cap screwed onto the ferrule, and a washer surrounding the blade and fixed thereto and against which fixed washer the slotted washer is clamped by the cap, the cap being provided with a sharp annular edge which bites down on the slotted washer to maintain a substantially gas-tight joint with said slotted washer, the slotted washer being out of sealing engagement with the end of the ferrule.

2. In a renewable electric fuse, the combination of a tubular shell of insulating material, a metallic ferrule fixed on the end of the shell and provided with a web which ex tends inwardly toward the axis of the ferrule andhaving its edge provided with an angular recess, a blade terminal having fixed thereto a transversely disposed abutment of proper periinetral shape, to fit into the recess in the web and thus prevent relative rotation between the blade terminal and the ferrule, a washer fixed on said blade terminal and arranged to overlap the edges of said recess from without to prevent an inward movement of the blade terminal relative to the ferrule, a slotted washer slipped over the outer end of the blade terminal, and an annular cap screwed onto the ferrule and clamping said slotted washer in position.

Signed at Tucson, Arizona, this 24th day of December, 1926.

1 FRANK O. LA MAR.

Ill 

